The relationship between the ratio of intensity of the third vibronic band to that of the first vibronic band in pyrene monomer fluorescence spectrum and its environmental polarity is used to probe the effects of alkali-metal chlorides MCl(M+ = Li+, Na+, K+) on the microenvironment of b-cyclodextrin (b-CD) cavity. Results reveal that the introduction of the salt decreases the polarity of b-CD cavity and increases the formation constant of pyrene-b-CD inclusion complex. It is indicated that hydrophobic interaction is one of binding forces of inclusion complex and that the salt, other than changing the ionic strength of the solution, interacts with b-CD mol., is the cause for the change in the microenvironment of b-CD cavity. The characteristics of the interaction between salt and b-CD are investigated in detail.

Key words: INFLUENCE, CYCLODEXTRIN, FLUOROSPECTROPHOTOMETRY, PYRENE, CAVITIES, INORGANIC SALT, ENVELOPMENT